A depolarization sensing threshold can be determined using an amplitude-limited portion of a cardiac signal received using an implantable medical device. One or more cardiac depolarizations can be detected using the cardiac signal and the depolarization sensing threshold.
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12. A method, comprising:
receiving a cardiac signal using an implantable medical device;
limiting an amplitude of the received cardiac signal to provide an amplitude-limited portion of the cardiac signal, wherein the amplitude-limited portion of the cardiac signal is amplitude-limited by one or more programmable thresholds;
determining a depolarization sensing threshold using the amplitude-limited portion of the cardiac signal, wherein the amplitude-limited portion of the cardiac signal used to determine the depolarization sensing threshold excludes one or more portions of the cardiac signal; and
detecting a cardiac depolarization using the cardiac signal and the depolarization sensing threshold.
1. An implantable medical device, comprising:
an input configured to receive a cardiac signal;
a first comparator configured to receive the cardiac signal from the input and to provide an amplitude-limited portion of the cardiac signal, wherein the amplitude-limited portion of the cardiac signal is amplitude-limited by one or more programmable thresholds;
a depolarization sensing threshold generation circuit configured to provide a depolarization sensing threshold using the amplitude-limited portion of the cardiac signal, wherein the amplitude-limited portion of the cardiac signal provided to the depolarization sensing threshold generation circuit excludes one or more portions of the cardiac signal; and
a depolarization detection circuit configured to detect a cardiac depolarization using the cardiac signal and the depolarization sensing threshold.
2. The implantable medical device of
wherein the cardiac signal includes the digital data.
3. The implantable medical device of
4. The implantable medical device of
5. The implantable medical device of
wherein the depolarization sensing threshold is substantially equal to at least one of the detected peak or the detected minimum of the amplitude-limited portion of the cardiac signal.
6. The implantable medical device of
7. The implantable medical device of
8. The implantable medical device of
9. The implantable medical device of
10. The implantable medical device of
wherein the one or more discrete steps includes a first depolarization sensing threshold provided at the beginning of the particular cardiac cycle, and a second depolarization sensing threshold equal to approximately 75% of the first depolarization sensing threshold.
11. The implantable medical device of
13. The method of
wherein the limiting the amplitude includes limiting the amplitude of the received cardiac signal to a percentage relative to the peak, the percentage specified using at least one programmable limit, to provide the amplitude-limited portion of the cardiac signal.
14. The method of
detecting at least one of a peak or a minimum of the amplitude-limited portion of the cardiac signal; and
providing, in response to the detecting, a depolarization sensing threshold substantially equal to at least one of the detected peak or the detected minimum of the amplitude-limited portion of the cardiac signal.
15. The method of
comparing the received cardiac signal with the depolarization sensing threshold; and
providing an event signal when the received cardiac signal exceeds the depolarization sensing threshold.
16. The method of
17. The method of
18. The method of
19. The method of
wherein the one or more discrete steps includes using a first depolarization sensing threshold, provided at the beginning of the particular cardiac cycle, and using a second. depolarization sensing threshold equal to approximately 75% of the first depolarization sensing threshold at a later time during the particular cardiac cycle.
20. The method of
receiving an analog signal representative of the cardiac activity; and
converting the analog signal into a digital signal using an analog-to-digital (A/D) converter.
21. The method of
receiving an analog signal representative of the cardiac activity; and
converting the analog signal into a digital signal using an analog-to-digital (A/D) converter having a single gain range without requiring clipping of the analog signal when the analog signal comprises both a depolarization of a typical amplitude and a depolarization of amplitude substantially greater than the depolarization of the typical amplitude.
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This patent application claims the benefit of priority, under 35 U.S.C. Section 119(e), to Seim et al., U.S. Provisional Patent Application Ser. No. 61/007,456, entitled “AUTOMATIC GAIN CONTROL TO LIMIT AMPLITUDE TRACKING,” filed on Dec. 12, 2007, incorporated herein by reference in its entirety.
Implantable medical devices (IMDs) can include cardiac rhythm management (CRM) devices such as pacemakers, cardioverter/defibrillators, and cardioverter/defibrillators with pacing capability, or one or more other types of devices. A CRM device can detect one or more dangerous cardiac arrhythmia conditions in the heart, such as a bradycardia, a tachycardia, a fibrillation, or one or more other arrhythmias such as by measuring the time interval between one or more consecutive cardiac depolarizations.
This overview is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application.
In an example, a depolarization sensing threshold can be determined using an amplitude-limited portion of a cardiac signal received using an implantable medical device. In an example, one or more cardiac depolarizations can be detected using the cardiac signal and the depolarization sensing threshold.
In Example 1, an implantable medical device can include an input configured to receive a cardiac signal, a first comparator configured to receive the cardiac signal from the input and to provide an amplitude-limited portion of the cardiac signal, a depolarization sensing threshold generation circuit configured to provide a depolarization sensing threshold using the amplitude-limited portion of the cardiac signal, and a depolarization detection circuit configured to detect a cardiac depolarization using the cardiac signal and the depolarization sensing threshold.
In Example 2, the input of Example 1 optionally includes an analog-to-digital (A/D) converter configured to convert an analog signal representative of cardiac activity into digital data, and the cardiac signal optionally includes the digital data.
In Example 3, the depolarization sensing threshold generation circuit of any one or more of Examples 1-2 is optionally configured to provide the depolarization sensing threshold at least in part using integer math.
In Example 4, the A/D converter of any one or more of Examples 1-3 is optionally configured to convert the analog signal into digital data using a single gain range without requiring clipping of the analog signal when the analog signal optionally includes both a depolarization of a typical amplitude and a depolarization of amplitude substantially greater than the depolarization of the typical amplitude.
In Example 5, the depolarization sensing threshold generation circuit of any one or more of Examples 1-4 optionally includes a peak detector configured to receive the amplitude-limited portion of the cardiac signal, to detect at least one of a peak or a minimum of the amplitude-limited portion of the cardiac signal, and to provide at least one of the detected peak or the detected minimum of the amplitude-limited portion of the cardiac signal to the depolarization sensing threshold generation circuit, and the depolarization sensing threshold is optionally substantially equal to at least one of the detected peak or the detected minimum of the amplitude-limited portion of the cardiac signal.
In Example 6, the depolarization detection circuit of any one or more of Examples 1-5 optionally includes a second comparator configured to compare the cardiac signal with the depolarization sensing threshold and to provide an event signal when the cardiac signal exceeds the depolarization sensing threshold.
In Example 7, the depolarization sensing threshold generation circuit of any one or more of Examples 1-6 is optionally configured to provide the depolarization sensing threshold to the detection circuit for a current cardiac cycle in response to the event signal.
In Example 8, the depolarization sensing threshold generation circuit of any one or more of Examples 1-7 is optionally configured to vary the depolarization sensing threshold level as a function of time during a particular cardiac cycle.
In Example 9, the depolarization threshold generation circuit of any one or more of Examples 1-8 is optionally configured to determine a depolarization sensing threshold peak value for a current cardiac cycle using a depolarization sensing threshold peak value from a previous cardiac cycle and the amplitude-limited portion of the cardiac signal.
In Example 10, the depolarization sensing threshold generation circuit of any one or more of Examples 1-9 is optionally configured to decrease the depolarization sensing threshold as a function of time, during the particular cardiac cycle, in one or more discrete steps following a piecewise linear approximation of a geometric progression, and the one or more discrete steps optionally include a first depolarization sensing threshold provided at the beginning of the particular cardiac cycle, and a second depolarization sensing threshold equal to approximately 75% of the first depolarization sensing threshold.
In Example 11, a method includes receiving a cardiac signal using an implantable medical device, limiting an amplitude of the received cardiac signal to provide an amplitude-limited portion of the cardiac signal, determining a depolarization sensing threshold using the amplitude-limited portion of the cardiac signal, detecting a cardiac depolarization using the cardiac signal and the depolarization sensing threshold.
In Example 12, the method of Example 11 optionally includes detecting a peak of a received cardiac signal during a particular cardiac cycle, and the limiting the amplitude optionally includes limiting the amplitude of the received cardiac signal to a percentage relative to the peak, the percentage specified using at least one programmable limit, to provide the amplitude-limited portion of the cardiac signal.
In Example 13, the determining the depolarization sensing threshold of any one or more of Examples 11-12 optionally includes detecting at least one of a peak or a minimum of the amplitude-limited portion of the cardiac signal, and optionally providing, in response to the detecting, a depolarization sensing threshold substantially equal to at least one of the detected peak or the detected minimum of the amplitude-limited portion of the cardiac signal.
In Example 14, the detecting the cardiac depolarization of any one or more of Examples 11-13 optionally includes comparing the received cardiac signal with the depolarization sensing threshold, and optionally providing an event signal when the received cardiac signal exceeds the depolarization sensing threshold.
In Example 15, the determining the depolarization sensing threshold of any one or more of Examples 11-14 optionally includes providing a depolarization sensing threshold substantially equal to at least one of the peak or the minimum of the amplitude-limited portion of the cardiac signal in response to the event signal.
In Example 16, the determining the depolarization sensing threshold of any one or more of Examples 11-15 optionally includes varying the depolarization sensing threshold as a function of time during a particular cardiac cycle.
In Example 17, the determining the depolarization sensing threshold of any one or more of Examples 11-16 optionally includes determining a depolarization sensing threshold peak for a current cardiac cycle using a depolarization sensing threshold peak value from a previous cardiac cycle and the amplitude-limited portion of the cardiac signal.
In Example 18, the determining the depolarization sensing threshold of any one or more of Examples 11-17 optionally includes decreasing the depolarization sensing threshold in one or more discrete steps following a piecewise linear approximation of a geometric progression, and the one or more discrete steps optionally include using a first depolarization sensing threshold, provided at the beginning of the particular cardiac cycle, and using a second depolarization sensing threshold equal to approximately 75% of the first depolarization sensing threshold at a later time during the particular cardiac cycle.
In Example 19, the receiving the signal of any one or more of Examples 11-18 optionally includes receiving an analog signal representative of the cardiac activity and optionally converting the analog signal into a digital signal using an analog-to-digital (A/D) converter.
In Example 20, the receiving the signal includes of any one or more of Examples 11-19 optionally includes receiving an analog signal representative of the cardiac activity, and optionally converting the analog signal into a digital signal using an analog-to-digital (A/D) converter having a single gain range without requiring clipping of the analog signal when the analog signal comprises both a depolarization of a typical amplitude and a depolarization of amplitude substantially greater than the depolarization of the typical amplitude.
In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
The present application incorporates U.S. Pat. No. 5,658,317, entitled “THRESHOLD TEMPLATING FOR DIGITAL AGC,” and assigned to Cardiac Pacemakers, Inc., by reference herein in its entirety.
Cardiac rhythm management devices can receive a sensed cardiac signal comprising electrical activity of the heart and detect cardiac depolarizations in the electrical activity when an amplitude of the electrical activity exceeds one or more predetermined amplitude levels or “sensing thresholds.” A depolarization sensing threshold can be fixed, or can be varied over time. The present inventors have recognized that a fixed depolarization sensing threshold can be inappropriate for detecting certain arrhythmias, such as polymorphic tachycardia, fibrillation, or premature ventricular contractions (PVCs) wherein extreme variations in the amplitude of the electrical activity can occur during the arrhythmia. For example, an amplitude of electrical activity associated with an arrhythmia such as polymorphic tachycardia, fibrillation, or a premature ventricular contraction can be substantially greater than a depolarization of typical amplitude. The problem of tracking variations in the amplitude of the electrical activity can be further complicated when the cardiac rhythm management device delivers pace pulses to the heart, which can cause evoked responses or one or more other electrical signals which are substantially higher than a typical amplitude associated with one or more intrinsic depolarizations.
The present application discloses, among other things, systems and methods to limit amplitude tracking for variable depolarization sensing threshold control. Certain embodiments of the present subject matter can include an A/D converter, such as with a single gain range, configured to cover the entire range of potentials representative of a cardiac signal representative of cardiac electrical activity (e.g., on the order of less than about 100 microvolts to on the order of about 25 millivolts or greater). Certain embodiments can include a 12-bit A/D converter. In an embodiment, one bit can be a sign bit, and the remaining eleven bits can be used as incremental values such as when converting one or more analog signals derived from the cardiac signal to one or more digital signals. In certain embodiments, the use of the single gain range to convert analog to digital can provide a digital signal more closely reflecting the actual cardiac signal waveform, showing amplitude or timing information with less distortion compared to the use of more than one gain range (e.g., without requiring clipping, or without inducing one or more other nonlinearities associated with using more than one gain range). Generally, in certain embodiments, the depolarization sensing threshold can be reactive to the peak value of the detected cardiac signal, a rolling average of previous cycles, or one or more other features or central tendencies of the detected cardiac signal. The present subject matter can be used to limit the change in a depolarization sensing threshold while still providing a depolarization sensing threshold reactive to a beat-to-beat variation, or one or more other variations in the detected cardiac signal. This can prevent the depolarization sensing threshold from being overly sensitive to abnormally high or low peaks in the detected cardiac signal, such as an abnormally high peak or an abnormally high amplitude associated with a premature ventricular contraction (PVC).
The CRM device 100 can be operated as a pulse generator device portion of a cardiac rhythm management system, and the system can also include one or more leads or electrodes disposed in, for example, the ventricular chamber of a heart to sense electrical activity representative of an R-wave portion of the PQRST complex indicating a depolarization in the ventricle as shown similarly on, for example, a skin surface electrocardiogram (EGM). The CRM device 100 can include one or more input/output terminals 101 which can be connectable to the one or more leads to receive, for example, an analog signal representative of the ventricular electrical activity of the heart sensed by the ventricular leads. A pace pulse circuit 102 can provide electrostimulation such as one or more of bradycardia or antitachycardia pacing pulses to the input/output terminals. In an embodiment, one or more electrostimulation pulses can be provided to the ventricular chamber of the heart via the ventricular leads to stimulate excitable myocardial tissue to treat arrhythmia conditions such as bradycardia, tachycardia, congestive heart failure, or one or more other heart-related diseases. A shock pulse circuit 103 can provide one or more shock pulses to input/output terminals, for example, to be provided to the ventricular chamber of the heart via the ventricular leads to shock excitable myocardial tissue to treat (e.g., defibrillate) tachyarrhythmia conditions. The tachyarrhythmia conditions can include ventricular fibrillation, or ventricular tachycardia, or one or more other conditions.
A filter and after-potential removal circuit 104 can be used to filter, for example, the ventricular electrical activity received by the input/output terminals 101, or the pacing pulses provided from the pacing pulse circuit 102. In addition, the filter and after-potential removal circuit 104 can remove after-potential created by, for example, a pacing pulse from the pacing pulse circuit 102 or a shock pulse delivered by the shock pulse circuit 103.
A filter and digitizing circuit 105 can be configured to transform the cardiac signal in one or more ways, such as by converting, processing, modifying or amplifying the filtered ventricular electrical activity provided from the filter and after-potential removal circuit 104. The filter and digitizing circuit 105 can include circuitry (e.g., an A/D converter or one or more other circuits), such as for digitizing the filtered ventricular electrical activity. An R-wave depolarization detection circuit 106 can be coupled to the filter and digitizing circuit 105, such as to detect depolarizations in the amplified ventricular electrical activity representative of R-wave depolarizations when the amplified ventricular electrical activity exceeds a selected amplified level known as a depolarization “sensitivity threshold” or a depolarization “sensing threshold,” and one or more refractories are inactive. A depolarization sensing threshold generation circuit, such as threshold generation circuit 107 can automatically select or adjust the depolarization sensing threshold. The R-wave depolarization detection circuit can provide an R-wave depolarization signal indicative of the R-wave depolarizations to, for example, a microprocessor or memory (e.g., microprocessor and memory 120).
The CRM device 100 can also include one or more leads or electrodes disposed in the atrial chamber of the heart, such as to sense electrical activity representative of a P-wave portion of the PQRST complex of a surface EGM indicating depolarizations in the atrium. The CRM device 100 can include one or more input/output terminals 111 connectable to the atrial leads, such as to receive the atrial electrical activity of the heart sensed by the atrial leads. A pace pulse circuit 112 can provide low voltage electrostimulation such as bradycardia pacing pulses to the input/output terminals 111, the electrostimulation to be provided to the atrial chamber of the heart via the atrial leads such as to stimulate excitable myocardial tissue to treat arrhythmia conditions such as bradycardia, atrial tachycardia, or one or more other conditions. A filter and after-potential removal circuit 114 can operate similarly to the filter and after-potential removal circuit 104, such as to filter the atrial electrical activity received by the input/output terminals 111 and the pacing pulses provided from the pacing pulse circuit 112. In addition, the filter and after-potential removal circuit 114 can remove the after-potential created by a pacing pulse from the pacing pulse circuit 112.
A filter and digitizing circuit 115 can be configured to transform the cardiac signal in one or more ways, such as by converting, processing, modifying or amplifying the filtered atrial electrical activity provided from the filter and after-potential removal circuit 114. The filter and digitizing circuit 115 can include circuitry (e.g. A/D converter, or one or more other circuits) for digitizing the filtered atrial electrical activity. A P-wave depolarization detection circuit can be coupled to the filter and digitizing circuit such as to detect depolarizations in the amplified atrial electrical activity representative of P-wave depolarizations when the amplified atrial electrical activity exceeds a selected amplified level known as a depolarization “sensitivity threshold” or a depolarization “sensing threshold” and one or more refractories are inactive. A depolarization sensing threshold generation circuit, such as threshold generation circuit 117 can automatically select or adjust the depolarization sensing threshold. The P-wave depolarization detection circuit can provide a P-wave depolarization signal, indicative of one or more P-wave depolarizations, such as to the microprocessor and memory 120 or one or more other portions, parts or components of CRM device 100. In certain embodiments, the microprocessor and memory 120 can then alter an operational mode of the CRM device 100 in response one or more sensed depolarizations such as to inhibit therapy delivery for one or more cardiac cycles (e.g., to suppress a pace pulse delivery when an intrinsic event is detected), or to initiate therapy delivery (e.g., to deliver a triggered pace pulse when an intrinsic event is detected), or to apply one or more detection methods to differentiate between one or more arrhythmias (e.g., to determine whether a tachycardia is occurring).
The microprocessor and memory 120 can analyze the detected P-waves, such as indicated in the P-wave depolarization signal from P-wave depolarization detection circuit, along with the R-wave depolarization signal provided from R-wave depolarization detection circuit, for the detection of one or more arrhythmia conditions using one or more arrhythmia detection algorithms. For example, the microprocessor and memory 120 can be used to analyze the rate, regularity, or onset of variations in the rate of the reoccurrence of one or more detected P-waves or R-waves, the morphology of one or more detected P-waves or R-waves, the direction of propagation of the depolarization represented by one or more detected P-waves or R-waves in the heart, or one or more other signals or parameters derived from information obtained from one or more physiologic sensors. In addition, the microprocessor and memory 120 can store depolarization data and, for example, can analyze one or more detected P-waves or R-waves to control one or more of a pace pulse circuit or a shock pulse circuit for delivery of pace pulses or shock pulses to a tissue site, such as the ventricle. In an example, the microprocessor and memory 120 can use one or more detected P-waves to control a pace pulse circuit for proper delivery of one or more pace pulses to the atrium. In an example, the microprocessor and memory 120 can include or control one or more state machines 108, such as to place one or more circuits of the CRM device 100 in one or more logical states based on various conditions such as when a pace pulse or shock pulse occurs or on operating conditions of the CRM device 100 such as bradycardia pacing, anti-tachyarrhythmia pacing, tachyarrhythmia sensing, normal sinus sensing, or one or more other operating conditions.
The A/D converter 221 can provide the stored digital data to an absolute value circuit 223, which can provide the absolute value of the amplitude of the digital data to, for example, the threshold generation circuit 107 or the threshold generation circuit 117, such as shown in the example of
In an example, the threshold generation circuit 107 or the threshold generation circuit 117, such as shown in the example of
In an example, the A/D converter 222 can process one or more cardiac signals (e.g., one or more intrinsic depolarizations, electrostimulations, PVCs or one or more other events) without clipping, such as by using a single gain range. The present inventors have recognized that at least one programmable limit (e.g. a programmable high limit 224 or programmable low limit 225, or one or more other limits) can be used to provide an amplitude-limited portion of the cardiac signal (e.g., a signal including an amplitude-limited by one or more thresholds) to the threshold generation circuit for use in providing the depolarization sensing threshold, or to limit a change in the depolarization sensing threshold. In the example shown in
In an illustrative example, a programmable high limit 224 can be an amplitude value, or can be a proportion, such as specified by a percentage. In this example, a proportion such as approximately 150% can be specified, and can limit the change used in the depolarization sensing threshold determination to 150% of the detected peak amplitude of one or more of the previous cardiac events (e.g., an R-wave, a P-wave, a PVC, or one or more other events occurring during a previous cardiac cycle). The present inventors have recognized that the threshold generation circuit need not overreact to a premature ventricular contraction (PVC), for example, or one or more other abnormally high amplitude sensed signals when the change used in the depolarization sensing threshold determination can be limited. In the absence of the programmable high limit and the limit to the change used in the depolarization sensing threshold determination, a CRM device 100, such as shown in the example of
In an illustrative example, a low limit can be approximately 50%, and can limit the change in the depolarization sensing threshold determination to 50% of the detected peak of the previous pulse. In the absence of the programmable low limit and limit to the change used in the depolarization sensing threshold determination, a CRM device 100, such as shown in the example of
Certain embodiments can adjust the depolarization sensing threshold based on a previous depolarization pulse (e.g., a peak amplitude of the most recent cardiac event as derived from a cardiac signal, or one or more other features of a previous pulse). Certain embodiments can adjust the depolarization sensing threshold based on a rolling average of a plurality of features of one or more preceding pulses. Certain embodiments can use an exponential average of one or more features of the previous pulses (e.g. ⅕ of the peak amplitude of the last beat +⅘ of the peak amplitude of one or more other preceding beats).
In an embodiment, the threshold generation circuit can decrease the variable depolarization sensing threshold in one or more discrete steps, or in a group of steps comprising multiple discrete steps of a fixed step size. In the embodiment illustrated in
When the variable depolarization sensing threshold decays to a programmable final value, such as specified by a programmable low limit, as indicated at 331, the threshold generation circuit can hold the variable depolarization sensing threshold at the programmable final value until one or more new sensed events occur. The programmable final value can be selected to compensate for noise which is inherent in the sense amplifiers, or other circuits included in the loop (e.g., the final value can be selected to minimize or eliminate spurious sensed events due to noise or the other circuits, or one or more other non-cardiac related events).
In an example, the initial drop percentage can achieve approximately 75% of the peak threshold value, and the four discrete steps in each step group can drop the variable depolarization sensing threshold to approximately 50% of the level of the starting threshold if the four-step group realizes a piecewise geometric progression linear approximation representing an exponential decay curve with minimal error between piecewise steps. Since the depolarization sensing threshold drops in discrete steps as indicated at 332, integer math can be used in the threshold generation circuit. For example in the embodiment of the threshold generation circuit illustrated in
In the example of
In certain examples, one or more of the input 401, the first comparator 426, the detection circuit 406, or threshold generation circuit 407 can be a portion, part or component of an integrated circuit, printed circuit assembly, or one or more other circuits, modules, components or portions included in the implantable medical device, such as the CRM device 100 shown in the example of
In an example, the threshold generation circuit 407 can include one or more peak detectors, the peak detectors coupled to the first comparator 426 can configured to receive the amplitude-limited portion of the cardiac signal. In this example, the one or more peak detectors can be configured to determine a peak or minimum value of the amplitude-limited portion of the cardiac signal, and in response, the threshold generation circuit can be configured to provide the peak or the minimum value as the depolarization sensing threshold to be used by, for example, the detection circuit 406.
At 504, an amplitude of the received cardiac signal can be limited to provide an amplitude-limited portion of the cardiac signal, such as by using one or more comparators such as a first comparator 426 as shown in the example of
At 506, the depolarization sensing threshold can be determined using the amplitude-limited portion of the cardiac signal. In certain examples, the depolarization sensing threshold for a current cardiac cycle can be determined using a peak or minimum value of the amplitude-limited portion of the cardiac signal corresponding to one or more previous depolarizations from one or more previous cardiac cycles. In certain examples, a moving average, weighted average, arithmetic mean, geometric mean, median, other central tendency, or one or more other features of one or more previous depolarizations included in the amplitude-limited portion of the cardiac signal can be used to determine the depolarization sensing threshold for the current cardiac cycle.
At 508, the cardiac signal can include one or more depolarizations, and the one or more depolarizations can be detected using the depolarization sensing threshold determined previously, such as at 506. In certain examples, the detecting the one or more depolarizations can use a detection circuit such as a detection circuit 406 as shown in the example of
A peak of the first variable depolarization threshold sequence 602A can be determined as the peak value of the first depolarization 601A. In some examples, a first peak of the first variable depolarization threshold sequence 602A can be a peak value of an amplitude-limited portion of the cardiac signal as shown in the examples of
The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown and described. However, the present inventors also contemplate examples in which only those elements shown and described are provided.
All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B.” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.
Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, the code may be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.
The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
Balczewski, Ron A., Seim, Gary T.
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Dec 05 2008 | BALCZEWSKI, RON A | Cardiac Pacemakers, Inc | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 022185 | /0399 | |
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